I have the Trains DVD, the Model Railroader DVD, and Model Railroader Special Issue collection:
1. Don't know. They are not accessable except by using the program supplied on the DVD
2. The program can be run from the DVD or it can be loaded onto the computer. If the files are resident on the computer, DVD does not have to be in the computer. This is the recommended way if you have the hard drive capacity, which probably most people do.
3. No, you don't have to be connected to the internet.
4. Don't know.
5. I like them, and find it easy to use after a little learning curve.
The thread linked has some of observations about the 75 Year Collection. Note that my initial comments about improperly scanned foldout pages, turned out to be Incorrect. The foldouts do not display properly in the 2-page view but are fine in the 1-page view.
http://cs.trains.com/mrr/f/88/t/212328.aspx
Some people do not like that the individual magazines cannot be saved for use in other applications.
To show the pages in my posts, I PRINT SCREEN and save them as jpg.
I tried to sell my two cents worth, but no one would give me a plug nickel for it.
I don't have a leg to stand on.